CN101452563B - Improved method for expanding and transforming jitter and modulating watermark - Google Patents

Abstract

The invention relates to an improved spread transform dither modulation (STDM) watermarking method and belongs to the technical field of digital watermarks. STDM watermarking has the combined advantages of quantization index modulation watermarking and a spread spectrum communication system, and high large watermark capacity and high robustness and has the disadvantage of high sensitivity to amplitude scaling attack. The invention constructs a signal invariable relative to the scaling for quantification by using a method which comprises: extracting from original content a statistical characteristic sequence which has a characteristic of scaling with original data according to the same scale factor; and obtaining the signal invariable relative to the amplitude scaling by dividing a carrier signal by the introduced characteristic sequence correspondingly. Watermark embedment and detection operation are both carried out on the newly constructed signal. The method improves the robustness of watermarks to amplitude scaling greatly and obtains watermarking performance similar to the original STDM watermarking in other aspects.

Description

A kind of improved method for expanding and transforming jitter and modulating watermark

Technical field

The invention belongs to the digital watermark technology field, be specifically related to a kind of improved method for expanding and transforming jitter and modulating watermark.

Background technology

Past 10 years, the use of digital media information and distribution explosive increase.By the internet, people can issue and obtain various numerical informations easily, comprise image, audio frequency, video and text etc., and many online services.But simultaneously, piracy also becomes and is more prone to, and unrestricted duplicating makes digital content have no copyright with uncontrollable transmission can to say.Management and protection to digital content become the problem that industry presses for solution.

Digital watermarking is a kind of emerging copyright protection technology.How its research hide a certain amount of additional information in raw data, the sign of the entitlement of works, the right to use or company etc. for example, and the purpose by the extraction that is hidden information and identification are reached the checking copyright.Digital watermarking has features such as fidelity, robustness, information capacity, reliability, security, blind Detecting and complexity.Except copyright protection, digital watermarking also can be used for digital signature, digital finger-print, broadcasting supervision, content authentication, copy control and secret communication etc.

Academia has proposed a large amount of water mark methods.Basically, they can be divided into two classes: a class is based on the water mark method of spread spectrum (SS:spread spectrum) modulation technique; One class is based on rejects the water mark method that carrier signal disturbs, for example quantization index modulation watermark (QIM:quantization indexmodulation).Though the SS water mark method has good anti-interference and compression performance, it can not remove the interference of carrier signal, and it is blind to detect right and wrong.In contrast, the QIM water mark method can be rejected the interference of carrier signal, has blind Detecting, and can obtain higher information capacity, thereby has received concern more and more widely.

Chen etc. have proposed QIM water mark method (seeing patent CN02115174.1).If A _oThe indicate original contents of embed watermark, it can be various types of signals, for example image, audio frequency or video etc.Through a signal extraction process, from original contents A _oIn extract the N carrier signal x that a length is,

Be used for embed watermark information m, wherein The expression set of real numbers.X can be one by original contents A _oThe vector formed of pixel value, perhaps by original contents A _oThe vector formed of any coefficient in transform domain etc.The basic thought of QIM watermark is to define plurality of sub-regions in the space of carrier signal x, and the corresponding different watermark informations of each subregion are modified in the corresponding subregion according to the value of the watermark information that will embed with x then; Watermark detection is the extracted region watermark information according to given carrier signal place.

Expanding and transforming jitter and modulating watermark (STDM:spread transform dither modulation) is a special case (the B.Chen et al..Achievable performance of digitalwatermarking Systems.Proc.IEEE Int.Conf.on Multimedia Computing andSystems of QIM water mark method, 1999, vol.1, pp.13-18), in the QIM digital watermark, occupy special status.The basic thought of STDM water mark method is to utilize the projection of jitter quantisation tolerance carrier signal on certain random direction to realize the embedding of watermark information.Particularly, the information m that STDM will embed is encoded into one and longly is the G metasequence b of p, its each element b _iSatisfy b _i∈ Ω, Ω=0,1 ..., G-1}; And for embedding the multidigit watermark information, carrier signal x is divided into p subsequence, i.e. x=x ₁|| x ₂|| ... || x _p, j sub-vector x wherein _jLength be L _j,

Produce one group of random number sequence isometric again, be designated as u, and it also is divided into p subsequence u=u with carrier signal ₁|| u ₂|| ... || u _p, its method of operating is identical with carrier signal.For the STDM of G unit, need to set up G

The jitter quantisation device

b _j∈ Ω.If use the uniform quantizer of quantization step, for the input vector of L dimension, jitter quantisation device as Δ

Central point may be defined as

Wherein,

The expression set of integers, I ^LBe that each element all is 1 L dimensional vector,

It is the security that a random vector is used to promote watermark.The Information Selection corresponding quantitative device that basis will embed when watermark embedded is for b _j, j=1 ..., p selects quantizer

Revise x _jAt u _jOn projection, promptly $y_j^T{u}_j=Q_{b_j}\left(x_j^T{u}_j\right),$ Y wherein _jExpression contains j the subvector of the carrier signal y of watermark.Thus, for y _j, can adopt along u _jDirection revise x _jMode obtain i.e. y _j=x _j+ α _ju _j, j=1 ..., p, wherein ${\mathrm{\α}}_j=q_{\mathrm{ej}}/u_j^T{u}_j,$ $q_{\mathrm{ej}}=y_j^T{u}_j-x_j^T{u}_j,$ Claim u _jBe spread vector, it has expressed the embedding direction of watermark.The signal y that use to obtain replaces x, utilizes the content A after the contrary leaching process of carrier signal obtains adding watermark then _wFor a data content A that will detect watermark, the STDM watermark detector uses with watermark and embeds the signal z to be detected that identical carrier signal leaching process obtains the distortion of a possibility, and when embedding the same p of a being divided into subvector and produce identical random vector u, re-use minimum distance criterion and extract from the projection on the corresponding subvector of u of each subvector of z and hide Info, promptly ${\hat{b}}_j=\arg \underset{b_j\∈\mathrm{\Ω}}{\min }|z_j^T{u}_j-Q_{b_j}\left(z_j^T{u}_j\right)|,$ j＝1，…，p。Another kind of realization is the method that watermark sequence b is embedded among the carrier signal x to generate p and the isometric and orthogonal spread vector of x, utilizes the projection of jitter quantisation tolerance x on each spread vector that each element of b is embedded in the carrier signal again.Certainly, watermark detector is also done corresponding the variation thereupon.

The STDM watermark effectively combines SS watermark and QIM watermark, has the advantage of the two concurrently, and not only watermark capacity is big, and anti-attack ability is strong, but a main weakness of quantisation watermarking is that the amplitude convergent-divergent is attacked very sensitivity.This is because when the amplitude of signal to be detected was scaled, the quantization step that is used to detect was not done corresponding convergent-divergent, thereby has produced matching error between water mark embedding device and detecting device, greatly reduces the performance of watermark.

J.J. dust Gus waits the method for estimation (seeing patent CN 02824865.1) that has proposed a kind of quantization step.This method is used to extract watermark information according to the quantization step that the histogram of signal sampling estimates after attacking through convergent-divergent.But, accomplish to estimate that accurately the data sample amount that needs is very big, be not suitable for the STDM watermark, and may introduce safe fragility.

A.A.C.M. card restrains the method for estimation (seeing patent CN02824950.X) of having invented another kind of quantization step.This method has been introduced a characteristic parameter, has and the carrier signal feature of the identical multiple of convergent-divergent simultaneously, utilizes the quantification after characteristic parameter is estimated to attack through convergent-divergent then.Yet, even this method is also non-vanishing in the error rate that does not have to detect under the condition of attacking.

A kind of water mark method (F.Perez-Gonz`alez et al..Rational dither modulation:A high-ratedata-hiding method invariant to gain attacks.IEEE Trans.SignalProcessing that is called Rational Dithered Modulation (RDM), vol.53, no.10, pp.39603975,2005.) adopted a quantization step that the amplitude convergent-divergent is had unchangeability at embedding device and detector end.Though RDM has obtained the robustness to the convergent-divergent attack, its performance depends on the memory capacitance of system, and approaches the performance of original jitter quantisation and watermark modulation along with the increase of memory capacitance, and at this moment, the system-computed amount has also increased.

Q. Lee waits resistivity (the Q.Li et al..Using perceptual models to improve fidelity and provideresistance to valumetric scaling for quantization index modulationwatermarking.IEEE Transactions on Information Forensics and Security that the Watson vision mode that has proposed application enhancements provides QIM that the amplitude convergent-divergent is attacked, vol.2, no.2, pp.127139, Jun.2007.).The performance of this method depends on human sensor model, thereby underaction, and the quality of carrier signal has been lost in the modification of sensor model than situation about not revising.

To sum up, in known quantisation watermarking technology, amplitude convergent-divergent attack problem is not well solved, and all there is corresponding deficiency in the several method that has had.

Summary of the invention

At the defective that exists in the prior art, the purpose of this invention is to provide a kind of improved STDM water mark method, this method is attacked the amplitude convergent-divergent has unchangeability, can obtain in other respects and the approximately uniform performance of original STDM watermark simultaneously.

For reaching above purpose, the technical solution used in the present invention is:

A kind of improved method for expanding and transforming jitter and modulating watermark, watermark embedding method is that one of structure has the signal of unchangeability and uses the STDM embed watermark information thereon the amplitude scale transformation, method of detecting watermarks is to utilize the STDM watermark detector to embed the signal that adopts same procedure to construct from one with watermark to extract watermark information, it is characterized in that watermark embedding method and method of detecting watermarks all comprise a signal configuration step that the amplitude scale transformation is had unchangeability.

Further, constructing one, the amplitude scale transformation is had method that the signal of unchangeability adopts is with element corresponding be divided by of carrier signal x with a characteristic sequence s, characteristic sequence s satisfies following character: when the amplitude of carrier signal is scaled, and the scaled together thereupon identical multiple of s.

Further, use the signal embed watermark information of STDM method operative configuration, then the signal that obtains and the corresponding element of characteristic sequence s are multiplied each other, obtain the carrier signal y of embed watermark.

Further, the method of watermark detection is to use with watermark and embeds identical method for extracting signal extraction carrier signal z and characteristic sequence s ' from the content of possibility distortion, corresponding element with the two is divided by then, and uses the STDM detecting device to extract watermark information from the signal that obtains.

Further, use certain statistic of data content, carrier signal x or their subvectors of wanting embed watermark, for example mean value, standard deviation value, Minkowski norm value etc. are formed sequences isometric with carrier signal, and the method for design feature sequence s is to make itself and aforementioned sequence in direct ratio.

Further again, be subjected to the influence of watermark embedding operation for avoiding characteristic sequence, the information that should select to have nothing to do with watermark embed process is come the structural attitude sequence.

Further again, when utilizing the information generating feature sequence of carrier signal, should reject the component of carrier signal on watermark embedding direction.

Further again, when adopting the information relevant to come the structural attitude sequence, can improve the performance of watermark with following compensation method with watermark embed process.Select several and watermark to embed the random vector of direction quadrature, and regulate the projection information of carrier signal on the random vector of each selection, make the watermark embedding front and back that are created in of characteristic sequence remain unchanged as far as possible, do not influence the performance of watermark detector simultaneously.

Further again, when adopting the mean value structural attitude sequence of carrier signal subvector, for promoting the performance of watermark, must be with the mean value cancellation of corresponding spread vector.

Effect of the present invention is: adopt method of the present invention, do not having under the situation of attacking, watermark detection can obtain the zero error rate; Can resist the amplitude convergent-divergent of any degree in theory and attack, attack has unchangeability to the amplitude convergent-divergent; The acquisition of this kind unchangeability does not rely on sensor model, thereby more flexible; Simultaneously, attack, can obtain the performance close with original STDM for other.

Description of drawings

The watermark flush mounting structural drawing of a kind of improved method for expanding and transforming jitter and modulating watermark of Fig. 1.

The watermark detection structure drawing of device of a kind of improved method for expanding and transforming jitter and modulating watermark of Fig. 2.

Fig. 3 amplitude convergent-divergent is attacked experiment.

Fig. 4 revises DC component and attacks experiment.

Fig. 5 Gaussian noise is attacked experiment.

The experiment of Fig. 6 JPEG compression attack.

Embodiment

Describe several specific embodiment of the present invention below in conjunction with accompanying drawing, and further specify effect of the present invention.

Embodiment 1:

With watermark carrier A _oBe a picture signal, realize a kind of improved STDM water mark method, watermark embed process may further comprise the steps as shown in Figure 1:

1) from A _oPiece DCT (DCT:Discrete Cosine Transform) territory extract carrier signal x.Earlier with A _oBe divided into a plurality of nonoverlapping sub-pieces, every contains 8 * 8 picture elements, carries out dct transform to every then.64 DCT coefficients in every are carried out the zigzag ordering, choose 62 DCT coefficients between the ordinal number 3 to 64.The DCT coefficient of all extractions is lined up a big sequence as carrier signal.Again the carrier signal that extracts is pressed certain random sequence scramble, generate final carrier signal and be designated as x, its length is N.This step is realized by the carrier signal draw-out device.

2) the information m that will embed is expressed as one and longly is the binary sequence b of p, wherein each element b _j∈ Ω, Ω=0, and 1}, j=1 ..., p.This step is realized by information representation and code device.

3) for the sake of simplicity, present embodiment is divided into p isometric subsequence with carrier signal x, is designated as x=x ₁|| x ₂|| ... || x _p, wherein

L is the length of each subsequence.Here, suppose that it is R=1/L that watermark embeds bit rate.

4) produce one group of L equally distributed random number as spread vector u.For the sake of simplicity, when present embodiment is the subvector embed watermark information of each carrier signal, use same spread vector u, and the average of u is converted into zero, i.e. E{u}=0, wherein function E{} represents mean value operation of vector.

5) calculated characteristics sequence s.From carrier signal, reject the component that embeds direction along watermark, can obtain and the irrelevant vectorial υ of watermark embed process.For x _j, j=1 ..., p can determine $v_j=x_j-x_j^T\mathrm{uu}/u^{T}u.$ Present embodiment adopts each subvector υ _jThe absolute value construction feature sequence s of mean value.Particularly, j the subvector s of characteristic sequence s _jBe taken as

s _j＝|E{υ _j}|I ^L (1)

This step is realized by the characteristic sequence generating apparatus.

6) each element of carrier signal x is constructed the signal that the amplitude scale transformation is had unchangeability divided by the corresponding element of characteristic sequence s, be designated as

$\tilde{x}=x./s---\left(2\right)$

This step is realized by the carrier signal converting means.

7) utilize the STDM method that each element of sequence b is embedded into signal

Corresponding subvector in obtain adding the signal of watermark

Be expressed as

${\tilde{y}}_j={\tilde{x}}_j+{\mathrm{\α}}_{j}u,j=1,\·\·\·,p---\left(3\right)$

α wherein _j=q _Ej/ u ^TU, $q_{\mathrm{ej}}=Q_{b_j}\left({\tilde{x}}_j^{T}u\right)-{\tilde{x}}_j^{T}u.$ This step information embedding device is realized.

8) with signal

The signal y that multiplies each other and obtain embed watermark with the corresponding element of characteristic sequence s, promptly

$y=\tilde{y}\·s---\left(4\right)$

This step is realized by the carrier signal inverter.

9) replace x with y, and carry out contrary extraction operation, comprise inverted disorderly, contrary ordering in a zigzag and contrary piece dct transform, the image that obtains containing watermark at last is designated as A _wThis step is realized by the contrary draw-out device of carrier signal.

A given picture signal A to be detected, watermark extraction process may further comprise the steps as shown in Figure 2:

1) extracts carrier signal z from piece DCT (the DCT:Discrete Cosine Transform) territory of A.This step is identical with the step 1 of watermark embed process, is realized by the carrier signal draw-out device.

2) step 3 with watermark embed process is identical, and carrier signal z is divided into p isometric subsequence, is designated as z=z ₁|| z ₂|| ... || z _p

3) produce spread vector u, method is identical with the step 4 of watermark embed process.

4) calculated characteristics sequence s '.Adopt the method identical to extract characteristic sequence with the step 5 of watermark embed process.If $v_j^{\′}=z_j-z_j^T\mathrm{uu}/u^{T}u,$ J=1 ..., p, j subvector s ' j of characteristic sequence s ' is taken as

s′ _j＝|E{υ′ _j}|I ^L (5)

This step is realized by the characteristic sequence generating apparatus.

5) each element of carrier signal z is constructed the signal that the amplitude scale transformation is had unchangeability divided by the corresponding element of characteristic sequence s ', be designated as

$\tilde{z}=z./s^{\′}---\left(6\right)$

This step is realized by the carrier signal converting means.

6) utilize the watermark detector of STDM method from signal

Each subvector in watermark information that extract to hide

Be expressed as

${\hat{b}}_j=\arg \underset{b_j\∈\mathrm{\Ω}}{\min }|{\tilde{z}}_j^{T}u-Q_{b_j}\left({\tilde{z}}_j^{T}u\right)|,j=1,\·\·\·,p---\left(7\right)$

This step information extracting device is realized.

7) with the watermark sequence that extracts

Obtain watermark information through decoding

This step is realized by information decoding device.

Be illustrated from principle below by the performance of present embodiment the water mark method of the present invention's proposition.

When the image that adds watermark did not suffer any attack, then the signal z that obtains by the carrier signal extraction element satisfied z=y.With this understanding, (3) are updated to v ' _jExpression formula in

υ′ _j＝υ _j，j＝1，…，p(8)

Equation (8) shows that vectorial υ is a vector that has nothing to do with watermark embed process.(1)-(6) and (8) are got in (7) for the people ${\hat{b}}_j=b_j,$ The error rate that is watermark detector is zero.Therefore, do not having under the situation of attacking, the same error rate that can both reach with original STDM of the method that present embodiment proposes is zero.In fact be that a kind of DM watermark with compensating distortion embeds expression formula, with its substitution (9), when weight vector υ selects must have when suitable ${\hat{b}}_j=b_j,$ The error rate that is watermark detector is zero.

Attack is insensitive to the amplitude convergent-divergent to refer now to the method why the present invention proposes.When carrier signal is exaggerated β doubly, i.e. z _j=β y _j, with (5) and (6) substitutions (7), factor-beta is cancelled as can be seen with it, and the extraction of watermark information and β are irrelevant.Therefore, the method for the present invention's proposition is attacked the amplitude convergent-divergent and is had unchangeability in theory, can resist the amplitude zoom operations of any degree.

Consider the additive noise passage, i.e. z=y+n.Get by (1) | E{ υ _j|=| E{x _j|, j=1 ..., p.Its substitution (5) is got | E{ υ ' _j|=| E{x _j}+E{n _j|, j=1 ..., p.This shows, when | E{x _j|＞＞| E{n _j|, j=1, during p, this normally sets up in actual applications, the variation of characteristic sequence this moment before and after attacking can be ignored the watermark Effect on Performance, and the bit error rate of watermark is mainly produced by noise, thereby the ability and the STDM of improved STDM water mark method opposing noise are approximately uniform.

In order to show remarkable result of the present invention, present embodiment provides some experimental results.Select 4000 width of cloth images to be used for test from the Corel database, every width of cloth size of images is 256 * 384.Therefore, for every width of cloth image, the carrier signal x that can to extract a total length in watermark embed step 1 be N=95232.The binary sequence b that length that produces at random is p=3072 is embedded in each width of cloth image as watermark information m, and wherein, per 31 DCT coefficients embed 1 bit information, i.e. L=31.Measure the picture quality spike signal to noise ratio (S/N ratio) (PSNR, peak signal-to-noise ratio) of embed watermark.The performance of the water mark method that provides by several typical attack experiment test embodiment.For convenience of description, the water mark method that embodiment is provided abbreviates IM-STDM as.Simultaneously, for purpose relatively, also provided STDM water mark method (B.Chen etal..Quantization index modulation:a class of provably good methodsfordigital watermarking and information embedding.IEEE Trans.Inform.Theory, vol.47, no.4, pp.14231443,2001.) and two kinds of improved jitter quantisation modulation (DM:dither modulation) water mark methods, promptly (abbreviate DM-MW and RDM-MW respectively as based on the DM of improved Watson vision mode and RDM based on improved Watson vision mode, please refer to document Qiao Li et al..Using perceptual models to improve fidelity and provideresistance to valumetric scaling for quantization index modulationwatermarking.IEEE Transactions on Information Forensics and Security, vol.2, no.2, pp.127139, Jun.2007.).In all experiments, PSNR is taken as 35dB, and this can realize by adjusting quantization step.The bit error rate that provides in the accompanying drawing is the mean value of gained test result on all images.

Fig. 3 has provided one group of amplitude convergent-divergent attack test result.In this respect, IM-STDM has obtained significant improvement performance with respect to STDM, and is better than DM-MW and RDM-MW.Particularly at the amplitude zoom factor less than 1.3 o'clock, IM-STDM has obtained the errors in zero level rate.

Fig. 4 has provided one group and has revised DC component attack test result.DC component is modified by the identical amount of the value increase/minimizing of each picture element of image.As can be seen, to this attack operation, IM-STDM is better than STDM slightly, and the two all is better than DM-MW and RDM-MW greatly from the figure.This is because the watermark embedding of IM-STDM and STDM and testing process are all irrelevant with the image DC component, and DM-MW and RDM-MW have used the DC component of image to obtain the robustness that the amplitude convergent-divergent is attacked, and the result has lost performance in this respect.

Fig. 5 has provided one group of Gaussian noise attack test result.Fig. 5 shows that IM-STDM has obtained the performance close with STDM, and all better than DM-MW and RDM-MW performance in this respect.As seen, even the latter two have used human sensor model, also be not so good as the performance of STDM.

Fig. 6 has provided one group of JPEG compression attack test result.Fig. 6 shows that the performance of STDM is better than IM-STDM and other two kinds of improved DM methods.Simultaneously, notice that the bit error rate of IM-STDM and the bit error rate of STDM are close for the bigger JPEG squeeze operation of quality factor.

The experimental result that present embodiment obtains can illustrate, uses method of the present invention not only to realize the robustness that the amplitude convergent-divergent is attacked, and has obtained and the approximately uniform performance of STDM watermark in other several typical attack operations.

Present embodiment has provided the implementation result of image watermark, handles but the invention is not restricted to image watermark, and the present invention is equally applicable to multimedia digital watermark processing such as digital music, video.

Embodiment 2:

Difference from Example 1 is,

In the step 5 of watermark embedding method, the method for calculated characteristics sequence s.The DC component of each 8 * 8 image subblock constitutes a vector, and this vector and watermark process are irrelevant.Present embodiment adopts this vectorial mean value, is designated as C00, construction feature sequence s.Particularly, characteristic sequence s is taken as

s＝C00I ^N

Simultaneously, in the step 4 of method of detecting watermarks, the method for calculated characteristics sequence s ' is also done corresponding modification.

Embodiment 3:

Difference from Example 1 is,

From carrier signal, reject the component that embeds direction along watermark, can obtain and the irrelevant vectorial υ of watermark embed process.For x _j, j=1 ..., p can determine $v_j=x_j-x_j^T\mathrm{uu}/u^{T}u.$ Present embodiment adopts each subvector v _jThe absolute value construction feature sequence s of mean value.Particularly, j the subvector s of characteristic sequence s _jBe taken as

In the step 5 of watermark embedding method, the method for calculated characteristics sequence s.Present embodiment adopts the standard deviation construction feature sequence s of each subvector of carrier signal.If function Var{} represents variance operation of vector.Particularly, j the subvector s of characteristic sequence s _jBe taken as

$s_j=\sqrt{\mathrm{Var}\left\{x_j\right\}}{I}^L$

In the step 7 of watermark embedding method, the signal of present embodiment after obtaining embed watermark

After, it is used following compensation scheme, make the watermark embedding front and back that are created in of characteristic sequence remain unchanged as far as possible, do not influence the performance of watermark detector simultaneously.Amount of orientation $v_j=x_j-x_j^T\mathrm{uu}/u^{T}u,$ J=1 ..., p, and

Change into ${\tilde{y}}_j={\tilde{x}}_j+{\mathrm{\α}}_{j}u+{\mathrm{\γ}}_j{v}_j,j=1,\·\·\·,p$

Select γ _jMake $\mathrm{Var}\left\{{\tilde{y}}_j\right\}=1$ Set up.Obviously, the compensation vector γ of increase _jυ _jCan not influence watermark detection.Simultaneously, in the step 4 of method of detecting watermarks, the method for calculated characteristics sequence s ' is also done corresponding modification.

The present invention can implement with other concrete form, and does not break away from its spirit or essential characteristic.It only is illustrative and nonrestrictive that described embodiment is considered in all respects, for example:

1) the carrier signal type is not limited to image, audio frequency and video etc.;

2) embed the territory and be not limited to DCT territory, Fourier transform domain, spatial domain and wavelet field etc.;

3) design of characteristic sequence is not limited to use mean value, standard deviation, and function such as various norms;

4) selection of various parameters etc.

Therefore, scope of the present invention by appended claims but not foregoing description indicate.Falling into the meaning of equivalence techniques scheme of claim and all changes of scope is included among its scope.

Claims (6)

1. improved method for expanding and transforming jitter and modulating watermark, watermark embedding method is a signal and the dithering modulation of watermarking of application extension conversion thereon STDM method embed watermark information that the amplitude scale transformation is had unchangeability of structure, method of detecting watermarks is to utilize the STDM watermark detector to embed the signal that adopts same procedure to construct from one with watermark to extract watermark information, it is characterized in that watermark embedding method and method of detecting watermarks all comprise a signal configuration step that the amplitude scale transformation is had unchangeability; Constructing one, the amplitude scale transformation is had method that the signal of unchangeability adopts is with element corresponding be divided by of carrier signal x with a characteristic sequence s, characteristic sequence s satisfies following character: when the amplitude of carrier signal is scaled, and the scaled together thereupon identical multiple of s; Use the signal embed watermark information of STDM method operative configuration, then the signal that obtains and the corresponding element of characteristic sequence s are multiplied each other, obtain the carrier signal y of embed watermark; The method of watermark detection is to use with watermark and embeds identical method for extracting signal extraction carrier signal z and characteristic sequence s ' from the content of possibility distortion, corresponding element with the two is divided by then, and uses the STDM detecting device to extract watermark information from the signal that obtains.

2. a kind of improved method for expanding and transforming jitter and modulating watermark as claimed in claim 1, it is characterized in that: certain statistic of using data content, carrier signal x or their subvectors of wanting embed watermark, comprise mean value, standard deviation value, Minkowski norm value, form a sequence isometric with carrier signal, the method for design feature sequence s is to make itself and aforementioned sequence in direct ratio.

3. a kind of improved method for expanding and transforming jitter and modulating watermark as claimed in claim 2 is characterized in that: be subjected to the influence of watermark embedding operation for avoiding characteristic sequence, the information of selecting to have nothing to do with watermark embed process is come the structural attitude sequence.

4. a kind of improved method for expanding and transforming jitter and modulating watermark as claimed in claim 3 is characterized in that: when utilizing the information generating feature sequence of carrier signal, reject the component of carrier signal on watermark embedding direction.

5. a kind of improved method for expanding and transforming jitter and modulating watermark as claimed in claim 2, it is characterized in that: when adopting the information relevant to come the structural attitude sequence with watermark embed process, improve the performance of watermark with following compensation method, select several and watermark to embed the random vector of direction quadrature, and the projection information of adjusting carrier signal on the random vector of each selection, make the watermark embedding front and back that are created in of characteristic sequence remain unchanged as far as possible, do not influence the performance of watermark detector simultaneously.

6. a kind of improved method for expanding and transforming jitter and modulating watermark as claimed in claim 5 is characterized in that: when adopting the mean value structural attitude sequence of carrier signal subvector, for promoting the performance of watermark, with the mean value cancellation of corresponding spread vector.

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